1. Field of the Invention
This invention relates to an analog-to-digital converting circuit generally shortened to an A/D converting circuit.
2. Description of the Prior Art
Typical A/D converting circuits include an array of voltage comparators which compare an input analog voltage with different reference voltages to convert the input analog voltage into a corresponding digital signal.
In the case where an input analog voltage to be converted is variable in a small range, it is known to provide an amplifier at a stage preceding a comparator array to amplify the input analog voltage before the execution of conversion thereof.
Most such amplifiers are unsuitable for use at high temperatures such as in automotive use. When such amplifiers are used at high temperatures, their operation tends to be wrong. Thus, it is generally difficult to use A/D converting circuits including amplifiers at high temperatures.